Wearable displays are an enabling technology for Virtual Reality (VR), Augmented Reality (AR), and 3D mobile displays. There are many wearable technologies that deliver a virtual image to the eye but they all require relay lenses between the display panel and the eye.
In the design of wearable displays, it is desired to have a large field-of-view (FOV) and a large exit-pupil-size (12-15 mm) to allow for eye-motion without losing the image. In the state of the art embodiments, there are some examples of head-mounted displays in military HMD's and virtual reality goggles with large FOV (up to 80° or 120°), but the optics are very bulky. Alternative approaches to reduce the size and bulk of the optics have exploited different solutions: (i) Active pupil-tracking is a promising solution but the optical mechanisms offered to track the pupil are quite complicated; (ii) Unconventional optical relays to make the optics more compact using light guides relays, holographic relays, or substrate guided relays, which are promising but still require a compromise in FOV to achieve the thin form-factor; (iii) Displays that require wearing a special contact lens. In the U.S. Pat. No. 8,441,731 developed a look-around novel display using self-emissive transparent OLED. Viewing the display requires a special contact lens with a high-diopter center lens and polarized filters: and (iv) Displays placed directly on contact lens, which would have limited resolution due to limited space. Furthermore, light emitted from individual emitters are not coherent and cannot be used to write an image on the retina due to diffraction from each emitter unless emitters are coupled by lenses or emit diffraction-free highly directional rays.
Wearable displays require optics to relay the image from the image generator to the eye as the eye cannot focus on a display that is placed in front of the eye which is at only few centimeters distance. The required relay optics and lenses are large and cannot be miniaturized due to various optical design constraints. Despite great advancements in micro-technologies, true breakthroughs in especially 3D wearable displays for mobile devices and Augmented Reality (AR) are missing due to two fundamental problems: (i) the relay lenses from the image source to the eye must remain large to provide a large field-of-view and 3D perception and (ii) viewing comfort is limited due to missing depth cues.